In summary, for patients who received video laryngoscopy:

Benefits in NNT

  • 7% lower rate of failed intubations
  • 9% lower risk of postintubation hoarseness
  • 3% lower risk of airway trauma
  • NNT of 14 for preventing failed intubation
  • NNT of 11 for preventing postintubation hoarseness
  • NNT of 37 for preventing airway trauma

Harms in NNT

    No identifiable harm
    No identifiable harms (no difference in the rate of hypoxia, sore throat, or mortality between the two groups)

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Source: Lewis SR, Butler AR, Parker J, Cook TM, Smith AF. Videolaryngoscopy versus direct laryngoscopy for adult patients requiring tracheal intubation. Cochrane Database Syst Rev 2016;11:CD011136.

Study Population: 7,044 adult patients (16 years and older) who required tracheal intubation across 64 trials

Efficacy Endpoints: Failed intubations, first successful attempts, airway trauma, postintubation hoarseness, and improved visualization

Harm Endpoints: Hypoxia, sore throat, and mortality

Narrative: Tracheal intubation is a critical step in securing the patient’s airway in a variety of emergent and nonemergent settings. Difficulties and complications may arise with this procedure, and alternative laryngoscopes that use video technology have been designed to improve visibility when airway difficulty is predicted or encountered. These devices may be flexible or rigid in design for the purpose of assisting in intubations, especially expected difficult intubations. Video laryngoscopes have been advertised as being able to reduce difficulty, failure, trauma, and other complications compared with direct laryngoscopy. Rigid video laryngoscopy uses a blade to retract the soft tissues and transmits a video image to a screen attached to the end of the handle or to a monitor. This design enables a lighted view of the larynx without direct “line of sight” and is also referred to as indirect laryngoscopy. In the Cochrane review discussed here,1 video laryngoscopy is compared to direct laryngoscopy in the tracheal intubation of adult patients.

The Cochrane review included randomized control trials of both parallel and crossover design. No simulation or manikin studies were included. Participants were aged 16 years and older who required tracheal intubation electively for scheduled surgery, as well as participants requiring emergent intubation in the emergency department (ED) or the intensive care unit (ICU). The included trials compared the use of a video laryngoscope (VLS) of any model versus direct laryngoscopy with a Macintosh blade.

Nine types of VLS designs were used in the 64 included studies: GlideScope, Pentax AWS, C-MAC (to include DCI laryngoscope), McGrath, X-lite, C-MAC D-blade, Airtraq, Truview EVO2, and CEL- 100. Most studies compared the use of GlideScope, Pentax AWS, C-MAC, and McGrath. Some designs of Airtraq and Truview EVO2 can be used with and without a camera attachment, so only those studies which used with a camera were included.

The meta-analysis showed statistically significant decrease in number of failed intubations when VLS was used (odds ratio [OR] = 0.35, 95 confidence intervals [CI] = 0.19–0.65, absolute risk difference [ARD] = 7%, number needed to treat [NNT] =14). However, the rate of successful first attempt intubation between the groups was not statistically significant (OR = 1.27, 95% CI = 0.77–2.09).

Subgroup analyses carried out by type of scope revealed no significant difference in the number of failed intubations when the GlideScope, Pentax, or McGrath were compared with the Macintosh blade. The result for failed intubation remained statistically significant in favor of the C-MAC device in this analysis. Another subgroup analysis was performed based on predicted or known difficulty airways. This subgroup analysis revealed that fewer failed intubations occurred when a VLS was used in predicted or known difficult airways (OR = 0.28, 95% CI = 0.15–0.55, ARD = 7%, NNT = 14, n = 830 patients).

The systematic review also demonstrated statistically significant reduction in likelihood of laryngeal/airway traumas (22 trials, OR = 0.68, 95% CI = 0.48–0.96, ARD = 3%, NNT = 37) and fewer incidences of postoperative hoarseness (six trials, OR = 0.57, 95% CI = 0.36–0.88, ARD = 9%, NNT 11) when a VLS device was used.

Additionally, the Cochrane review analyzed intubation difficulty scale (IDS) and airway visualization. IDS scores were recorded in seven studies with 0 representing no difficulty. VLS increased the likelihood of a reported intubation difficulty scores of 0. Airway visualization was evaluated using Cormack-Lehane views. Achieving a Cormack-Lehane grade 1 view was also more likely with VLS.

Caveats: The use of video laryngoscopy was not adequately explored in the emergency setting. Of 64 studies included in the meta-analysis, only three studies included participants requiring emergency intubation (one in the ICU, one in the ED, and one in an out-of-hospital setting). Therefore, the findings of this systematic review might not be generalizable to emergency settings.

All studies were subject to a high level of bias due to the inability to blind personnel to the type of laryngoscope used with each participant. As a result, the Cochrane authors downgraded the evidence for each outcome by one level for study limitations. Failed intubation, proportion of successful first attempts, and sore throat outcomes were assessed to be moderate-quality evidence, whereas outcomes of hypoxia, serious respiratory complications, and mortality were downgraded to very-low-quality evidence for imprecision. Additionally, a large number of studies with substantial heterogeneity that reported time to tracheal intubation were downgraded to very-low-quality evidence.

Most studies used an experienced anesthetist to perform laryngoscopies. However, it was not always clear from the papers whether anesthetists had equivalent experience with both devices. In light of improved patient centered outcome and relative safety, we assign a color recommendation of green (benefits > harms) to this intervention.

The original manuscript was published in Academic Emergency Medicine as part of the partnership between TheNNT.com and AEM.

Author: Abdullah Bakhsh, MBBS, FAAEM; Michael Ritchie, MD
Supervising Editors: Shahriar Zehtabchi, MD; Jarone Lee, MD

Published/Updated: March 4, 2019

  1. The Title Bar

    The title bar is color-coded with our overall recommendation.

    • Green: Benefits outweigh risks.
    • Yellow: Unclear risk/benefit profile.
    • Red: Benefits do not outweigh risks.
    • Black: Obvious harms, no clear benefits.
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